<h1 id="dmesg">dmesg</h1>
<p>显示Linux系统启动信息</p>
<h2 id="补充说明">补充说明</h2>
<p><strong>dmesg命令</strong> 被用于检查和控制内核的环形缓冲区。kernel会将开机信息存储在ring buffer中。您若是开机时来不及查看信息，可利用dmesg来查看。开机信息保存在<code>/var/log/dmesg</code>文件里。</p>
<h3 id="语法">语法</h3>
<pre><code class="language-bash">dmesg(选项)</code></pre>
<h3 id="选项">选项</h3>
<pre><code class="language-bash">-c：显示信息后，清除ring buffer中的内容；
-s&lt;缓冲区大小&gt;：预设置为8196，刚好等于ring buffer的大小；
-n：设置记录信息的层级。</code></pre>
<h3 id="实例">实例</h3>
<pre><code class="language-bash">[root@localhost ~]# dmesg | head
Linux version 2.6.18-348.6.1.el5 (mockbuild@builder17.centos.org) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)) #1 SMP Tue May 21 15:34:22 EDT 2013
BIOS-provided physical RAM map:
 BIOS-e820: 0000000000010000 - 000000000009f400 (usable)
 BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 000000007f590000 (usable)
 BIOS-e820: 000000007f590000 - 000000007f5e3000 (ACPI NVS)
 BIOS-e820: 000000007f5e3000 - 000000007f5f0000 (ACPI data)
 BIOS-e820: 000000007f5f0000 - 000000007f600000 (reserved)
 BIOS-e820: 00000000e0000000 - 00000000e8000000 (reserved)</code></pre>
<p>查看硬盘基础信息</p>
<div class="sourceCode" id="cb4"><pre><code class="language-bash"><a class="sourceLine" id="cb4-1" data-line-number="1"><span class="fu">dmesg</span> <span class="kw">|</span> <span class="fu">grep</span> sda</a>
<a class="sourceLine" id="cb4-2" data-line-number="2"></a>
<a class="sourceLine" id="cb4-3" data-line-number="3"><span class="bu">[</span>    2.442555] sd 0:0:0:0: [sda] 488281250 512-byte logical blocks: (250 GB/232 GiB)</a>
<a class="sourceLine" id="cb4-4" data-line-number="4">[    2.442590] sd 0:0:0:0: [sda] Write Protect is off</a>
<a class="sourceLine" id="cb4-5" data-line-number="5">[    2.442592] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00</a>
<a class="sourceLine" id="cb4-6" data-line-number="6">[    2.442607] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn<span class="st">&#39;t support DPO or FUA</span></a>
<a class="sourceLine" id="cb4-7" data-line-number="7"><span class="st">[    2.447533]  sda: sda1</span></a>
<a class="sourceLine" id="cb4-8" data-line-number="8"><span class="st">[    2.448503] sd 0:0:0:0: [sda] Attached SCSI disk</span></a></code></pre></div>
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